1. Field of the Invention
This invention relates to a manually portable film holder which provides a lighttight environment for photographic film. A film unit inside an opaque envelope, which may also include a conventional darkslide, may be inserted through an opening in one sidewall of the film holder, and after the unit is enclosed within the lighttight environment of the holder, the envelope (and/or the darkslide) is retracted, thereby uncovering the film unit for exposure to light or to some other type of electromagnetic radiation. A preferred source of electromagnetic radiation comprises an electrophoresis gel mounted on a block within the lighttight film holder. The electrophoresis gel is reciprocable into and out of surface contact with the film unit to allow the exposure to electromagnetic radiation from an isotope or chemiluminescence label. The gel is pressed against the photosensitive material of the film unit for a predetermined period of time, and after that time period has elapsed the gel is retracted from the film unit, the envelope (or the dark slide) is then reinserted to cover the exposed film, and the envelope and film unit are extracted from the holder for subsequent instant or non-instant type developing.
2. Description of the Prior Art
Film holders for instant or self-developing, peel-apart, sheet film are numerous. The holders may be either a separate opaque film holder or a camera back which allows for loading of film into the lighttight holder for subsequent exposure by some specified means while within the holder.
A particular problem involves the exposure of a film unit by an electrophoresis gel containing a DNA or a protein material while within a lighttight environment for some specified period of time which may be for minutes or days, depending upon various physical properties. The exposed film unit is developed by conventional methods and the photographic image of the DNA material is then available for subsequent analysis of the associated DNA sequencing defining such material.
Custom made electrophoresis gel, in sheet form, is presently available from a number of suppliers. A customer who might be interested in the DNA sequencing of some animal tissue, fluid, etc. may send the material in question to the supplier for inclusion in an electrophoresis gel. A part of the process of preparing the gel is to place the submitted material that includes the particular isotope or chemiluminescence label on a gel which is appropriate for the particular material. An electrical current is then passed through the gel to properly distribute or orient the DNA for subsequent image transferring purposes. The gel is then formed into a solid sheet-like material which is then returned to the customer. The process for formation of the gel is well known and is not a part of this invention.
At the present time DNA images are formed on film by placing the electrophoresis gel against a sheet of photosensitive material and maintaining them in firm contact for the specified period. The placement of the electrophoresis gel against the photosensitive material and the image transferring process must take place in a darkroom to prevent inadvertent exposure of the film unit. This is obviously a difficult and time consuming chore. There is a need for an apparatus which provides a manually portable film holder-darkroom which allows the photosensitive film unit to be handled in ambient light. A manually portable film holder which will allow the daylight insertion of a film unit into the holder combined with a means to press the electrophoresis gel against the photosensitive material while within the film holder is desirable.
U.S. Pat. No. 3,747,496 discloses a film unit in an opaque envelope, a means for opening the envelope while it is inside a camera, taking a photograph to expose the film unit, reinserting the envelope into the camera around the exposed film unit, and removing the envelope to allow the film unit to develop. This broad technique has been well known for many years. U.S. Pat. Nos. 4,804,989; 4,833,493; and 4,903,063 all disclose alternative structures involving means for exposing a film unit in a particular film holder environment. Various structures are shown in those patent disclosures and drawings for maintaining a lighttight environment during the whole procedure.
U.S. Pat. No. 2,450,841 discloses a film holder for use in the photographic industry and a peripheral structure around the edge of the two mating parts of the film holder includes a tongue-in-groove arrangement to prevent the incursion of light from the mating sides of the two parts of the film holder.
U.S. Pat. No. 2,834,271 discloses the use of pile fabric around an exit from a film holder where the film unit passes through an opening lined with pile fabric. The pile fabric allows the film unit to slip through the opening while the pile fabric is displaced and without allowing light to penetrate.
In an electrophoresis gel application involving pressing the gel against photosensitive material, the means for achieving the pressure required is a consideration and U.S. Pat. No. 2,709,223 shows a technique for applying pressure against a photosensitive sheet.